Vertical-axis wind turbine



FIG. 1 is a perspective view of a vertical-axis wind turbine comprising the new design;

FIG. 2 is a front elevation view thereof, where the rear, left and right elevation views are mirror images thereof;

FIG. 3 is a top plan view thereof; and,

FIG. 4 is a bottom view thereof.

The broken lines shown represent unclaimed subject matter and form no part of the claimed design. 

The ornamental design for a vertical-axis wind turbine, as shown and described. 